1. Field of the Invention
The present invention generally relates to an expansion nozzle for a rocket engine required to function successively under atmospheric and space conditions, and more particularly relates to an expansion nozzle comprised of a main wall defining a surface of revolution that splays outwardly between a nozzle throat and a downstream extremity of said nozzle.
2. Background of the Invention
In rocket engines, an expansion nozzle is the part of the rocket engine's main nozzle that serves to transform the energy produced in the combustion chamber into an impulsive force by transforming the potential energy contained in combustion gases under pressure into kinetic energy. The efficiency of this transformation process improves as the pressure drop in the expansion nozzle increases. The pressure drop is determined by the ratio between the flow section at the expansion nozzle's exhaust port and to the flow section at the throat section of the main nozzle.
For engines operating at ground level, i.e. with an atmospheric pressure of around one bar, or in the presence of a counter-pressure, the above pressure drop is limited by the condition of burble-free flow of the gas jet in the expansion nozzle, which imposes a minimum value Pe/Pa for the ratio between the pressure Pe exerted on flow-containing walls by the exhausted gases and atmospheric pressure Pa. Known rocket engine exhaust nozzles for ground level operation have flow sections that are limited by the above burbling effect. As a consequence, they give relatively poor performance at altitude.
The object of the present invention is to increase the pressure drop obtainable by an expansion nozzle having to operate at ground level or in the presence of a counter pressure by means of an easily installable device.